Ophanin

Ophanin is a toxin found in the venom of the King Cobra (Ophiophagus hannah), which lives throughout South East Asia.

Ophanin weakly blocks the contraction of smooth muscles elicited by high potassium-induced depolarization,[1] suggesting that it inhibits voltage-dependent calcium channels.

[1] Ophanin, along with other specific snake toxins like triflin and ablomin, is also a helothermine-related venom protein (Helveprin) which was originally isolated from the skin of the Mexican beaded lizard.

Snake venom CRISP family proteins inhibit depolarization-induced smooth muscle contraction to different extents.

However, it is likely that the picture is more complex and other residues contribute to the inhibitory activity of CRISPs on smooth muscle contraction and some data supports this.

However, based on the hypothesis of Yamazaki and colleagues[6] in regards to ablomin, another snake venom toxin from the CRISP family that also blocks depolarization-induced smooth muscle contraction, we can postulate a similar mechanism might be in place for ophanin.